A key switch device includes a base plate, a sheet laminated on the base plate, a key top disposed above the sheet, a rubber dome that is disposed between the sheet and the key top and presses the sheet in a case where the key top is pressed down, and a guide mechanism that is foldably mounted between the base plate and the key top and supports the key top so as to be movable up and down.
Incidentally, if a small keystroke of the key switch device described above is made, even when the center of the key top is pressed down, the lower end face of the key top or a portion of the guide mechanism approaches to the extent that it comes into contact with the sheet laminated on the base plate. Therefore, when a portion distant from the center of the key top is pressed down, the lower end face of the key top or a portion of the guide mechanism impacts against the sheet laminated on the base plate. Since impact when the lower end face of the key top or a portion of the guide mechanism impacts against the sheet laminated on the base plate is equal to impact when the lower end face of the key top or a portion of the guide mechanism impacts against the base plate and is turned into a bottom-out feeling, thereby being transmitted to the finger that operates the key top, so is undesirable.
In order to suppress such a bottom-out feeling when operating a key, providing a gap between an upper sheet and a lower sheet which constitute the sheet, at the portion corresponding to the lower end face of the key top of the sheet, has been proposed (Japanese Patent Application Laid-Open No. 2001-184979).